Search Results: "ed"

23 November 2012

Tanguy Ortolo: Mobile browsers, you suck (or: RTFM CSS media type)

Mobile devices A number of people are using small mobile devices to read Web pages. These devices have small screens, which make it hard to read pages designed for a large screen width.CSS Media types to the rescue Good news: the W3C thought of that fourteen years ago, when they introduced the concept of media types in CSS 2: 
<link rel="stylesheet" type="text/css" media="handheld"/>
Here, the attribute media="handheld" indicates this dedicated style sheet should be loaded by hand-held devices (typically small screen, limited bandwidth) (quoting the CSS 2.1 Specification). Cool stuff, for a specification written in 1998, is it not? or not Well, bad news: mobile browsers do not honour it. Try this test page with a hand-held device: if the browser respects the specification, it should display a section of text which is not shown for regular browsers. It probably wont. So, how do people do to implement a specific style for mobile devices? Well, the W3C seemed to acknowledge the fact that mobile browser authors had no intention of respecting the existing specification, so they extended it with Media Queries: 
<link rel="stylesheet" type="text/css" media="screen and (max-device-width: 480px)"/>
Here, this attribute indicates this dedicated style sheet is to be loaded by devices with a screen not too large (in pixels: not sure how this would work with small but high resolution screens). Thank you, mobile browsers, for not implementing a specification that was designed just for you before you even existed, and requiring such a kludge with a new specification instead

Keith Packard: MicroPeak

MicroPeak tiny peak-recording altimeter now available MicroPeak is a miniature peak-recording altimeter. About the same size and weight as a US dime (with battery), MicroPeak offers fabulous accuracy (20cm or 8in at sea level) and wide range (up to 31km or 101k ). The size of the board was predicated with the premise that we needed a battery included to avoid having wiring running between the altimeter and the board, we found some small lithium coin-cell battery holders for the CR1025 battery. These battery holders are rated to hold the battery secure up to 150gs. We d already started playing with the Measurement Specialties MS5607 pressure sensor which offers amazing accuracy while using very little power. Taking full-precision measurements every 96ms consumes about .2mA on average. Once on the ground, we stop taking measurements entirely, dropping the power use to around 1 A. It s also pretty small, measuring only 5mm x 3mm. For a CPU, this little project didn t need much. The 8-bit ATtiny85 comes in a 20qwfn package which is only 4mm x 4mm. When run at full speed (8MHz), it consumes a couple of mA of power. Reduce the clock to a pokey 250kHz and the CPU has enough CPU power to track altitude while consuming less than .2mA on average. To avoid losing the battery, we wanted to avoid having it removed while the board wasn t in use. So, we added a little power switch to the board. The one we found is good to at least 50g. Finally, we wanted to find a nice bright LED to show the state of the device and to blink out the final altitude. The OSRAM LO T67K are bright-orange surface-mount LEDs that run happily on 2mA. We used OSHPark.com to create prototype circuit boards for this project. Because of the small size of the board, each prototype run cost only $2 for three boards. It takes a couple of weeks to get boards, but it s really hard to beat the price. All of the schematic and circuit board artwork are published under the TAPR Open Hardware License and are available via git. All of the source code is published under the GPLv2 and is included in the main AltOS source repository.

22 November 2012

Bdale Garbee: Shiny Black Friday

Altus Metrum is pleased to announce our first-ever "Shiny Black Friday" event! We're combining a special, one-time discount on TeleMini products with a price reduction on TeleMetrum boards ... and a new product introduction! For one day only, Friday, 23 November 2012, we are offering a special $50 discount on TeleMini Starter Kits (regular $225, now only $175!) and TeleMini boards (regular $125, now only $75!). This discount is available only for direct orders from our web site, see below. TeleMini is a baro-only recording dual deployment altimeter with radio telemetry and direction finding features. Learn more about TeleMini at We are also pleased to announce that TeleMetrum is back in stock after a brief production delay. To celebrate, we are dropping the price of extra TeleMetrum boards from $350 to $325. Starter kits will continue to sell for $400. TeleMetrum is a dual-deploy altimeter with accel and baro sensors, GPS, and radio telemetry and direction finding features all on one board! Learn more about TeleMetrum at Last, but certainly not least (unless we're talking size or mass!), we are proud to introduce a new product... MicroPeak! MicroPeak is a tiny board that provides highly accurate peak barometric altitude recording. About the size and weight of a US dime with battery ready to fly (18x14mm, 1.9 grams), this is the ideal altimeter for model rocket contests. MicroPeak is so easy to use that it's also the ideal altimeter for young people working on rocket related science fair projects, etc! MicroPeak sells for $50, learn more at Find more information on all Altus Metrum products at http://altusmetrum.org. The special Black Friday discount on TeleMini products is available only on orders placed through Bdale's web store at http://auric.gag.com. Thank you for making 2012 such a great year for Altus Metrum, LLC. We're having fun, and look forward to introducing several exciting new products in the weeks and months ahead!

Philipp Kern: OpenClonk

The Free and Open successor to the Clonk computer game series OpenClonk is now available in Debian sid and Ubuntu raring: just use sudo apt-get install openclonk to install it (backports to Ubuntu precise and quantal can be found in the OpenClonk Releases PPA).

<iframe allowfullscreen="allowfullscreen" frameborder="0" height="236" src="https://www.youtube.com/embed/ykJZ9WsevGE" width="420">OpenClonk Beyond the Rocks Trailer</iframe>

It's still under development, but as you can see it's also already quite functional. The engine was made available freely under the ISC license after the original author of Clonk was no longer interested in creating new successors. Many of the old volunteer contributors then picked it up. Be aware that same computer multiplayer, which was available in the older parts of the series, is gone. If you play on the network, you need to ensure that both of you have the same version of the game.

Andrew Pollock: [life] Portland bound

So, after just having run 10K, I'm going to sit on a train for 20 hours and completely seize up. I've got me some stretching to do! I'm getting away to Portland for a few days. I'm taking the Coastal Starlight train up and back, and staying with Nigel and his family. I'm looking forward to having some time to myself on the train, I'm looking forward to the trip, because some mutual friends did it, and I've wanted to do it ever since. I'm also looking forward to catching up with Nigel, because I've barely spoken to him since he left Google, and he's a friend and fellow countryman who I really enjoyed working with. I'd also like to check out this barber shop, because I'm weird and like the idea of someone attacking my face with a cutthroat razor. And of course, you can't go to Portland without visiting Powell's City of Books. I'm probably spending as much time on the train as I am in Portland (I head back on Sunday), but I want to be back for Zoe's first dentist appointment on Tuesday.

Andrew Pollock: [life] Silicon Valley Turkey Trot

Sarah, Zoe and I ran in the 10K Applied Materials Silicon Valley Turkey Trot this morning. Apparently it's a bit of a Silicon Valley institution (people get dressed up, particularly as turkeys), so I guess it's up there with the Bay to Breakers. This is the first time I've ever run a 10K fun run and actually run the whole way, so I'm feeling pretty happy with my fitness. In fact, I think I'm the fittest and lightest I've ever been. I'm actually a couple of kilograms under my target weight, and really pleased with myself for being able to run a 10K training run on Tuesday as well as the race today. I managed to run it in a respectable 1:05. I think I'll set a goal for myself to be able to run 10K in under an hour. No idea if that's realistic or not, but it's a goal with a nice round number. Sarah did her run in 1:06, which is impressive considering she was pushing Zoe in the jogging stroller. Zoe also did well putting up with being in the jogging stroller for that long. I think it helped having lots of things for her to look at, as well as a steady supply of food to graze on. She was having a great time running on the closed streets as we headed back to where we parked the car. We might have to make this a Thanksgiving family tradition. It'll be nice when Zoe's big enough to run in the kid's fun run as well.

Andrea Veri: The Linux s perception of my neighbours

I live in a little village close to the city and one of the houses close to my property is for rent since more than ten years. A lot of families and people succeeded in that house and every time someone new joined my Linux evangelist hat jumped in my head. I ve always presented myself as a Linux geek to my neighbours and it has been nice seeing how the Linux word evolved (with funny and surprising quotes) during the past ten years in their minds. A friend of mine (Aretha Battistutta) made a little comic strip out of the topic and the result is simply amazing. Enjoy!

Josselin Mouette: Fun with automated translations

Today I tried to translate a German sentence posted by mistake on an English IRC channel. For that, I used Google translation. I think there is a message here about what country KDE comes from

Ian Wienand: Upgrading Samsung Series 9 Laptop BIOS without Windows

Having recently acquired a Samsung Series 9 laptop, I'd like to update the BIOS. This is proving rather difficult without Windows. The first thing you download from the Samsung website isn't actually BIOS update at all; it's a Windows application which then goes and finds a BIOS update for your machine. Some time with a Windows VM, tcpdump and you'll end up at http://sbuservice.samsungmobile.com/. I'll leave interested parties to play around at that website, but with a little fiddling you can find the BIOS you're looking for. In this case, it is ITEM_20121024_754_WIN_P08AAH.exe which is the latest version, P08AAH. Unfortunately, this still won't run in any useful way -- in a virtual-machine it errors out saying the battery isn't connected. On previous endeavors such as this, running various incarnations of zip on the .exe file has found interesting components, but not in this case. Not to be deterred, some work with strings will yield the following 
$ strings ./ITEM_20121024_754_WIN_P08AAH.exe   grep Copyright
inflate 1.2.7 Copyright 1995-2012 Mark Adler
deflate 1.2.7 Copyright 1995-2012 Jean-loup Gailly and Mark Adler
Now this is interesting, because it tells us that the components aren't using some fancy compression scheme we have no hope of figuring out. Checking RFC1952 we see the following header mentioned 
Each member has the following structure:
+---+---+---+---+---+---+---+---+---+---+
 ID1 ID2 CM  FLG      MTIME      XFL OS   (more-->)
+---+---+---+---+---+---+---+---+---+---+
We can easily look for that in the file. Expanding the values, what we're looking for is 0x1f 0x8b 0x08 0x0 0x0 0x0 0x0 0x0 0x0 0x0 which represents the compressed stream (the OS byte is 0xb for NTFS which we can just ignore). A quick hack will get that done and give us the offsets we need 
$ ./look-for-headers
Found potential header at 455212
Found potential header at 677136
Found potential header at 1293930
Found potential header at 1294980
Found potential header at 2771193
Found potential header at 2779874
Found potential header at 2789142
Found potential header at 2935778
Found potential header at 3078639
Found potential header at 3083039
Found potential header at 3338552
Found potential header at 3339443
Found potential header at 3352440
Found potential header at 3366757
Found potential header at 3391734
Found potential header at 3444255
Found potential header at 3494372
So, we can feed this into a shell script and extract the streams 
FILE=ITEM_20121024_754_WIN_P08AAH.exe
for offset in 455212 677136 1293930 1294980 \
    2771193 2779874 2789142 2935778 3078639 \
    3083039 3338552 3339443 3352440 3366757 \
    3391734 3444255 3494372
do
    echo "create $offset.gz"
    dd if=$FILE  bs=1 skip=$offset   zcat > $offset.data
done
We don't have to worry about the end-point, because zcat will handily stop outputting and ignore junk at the end of the stream. That will yield the following output files: 
$ md5sum *
c014e900b02ae39d6e574c63154809b2  1293930.data
982747cd5215c7d51fa1fba255557fef  1294980.data
942c6a8332d5dd06d8f4b2a9cb386ff4  2771193.data
d98d2f80b94f70780b46d1f079a38d93  2779874.data
33ce3174b0e205f58c7cedc61adc6f32  2789142.data
1d6851288f40fa95895b2fadee8a8b82  2935778.data
3a0a9b2fa9b40bdf5721068acde351ce  3078639.data
fc166141d06934e9c7238326f18a4e68  3083039.data
8cf7f86f84afa81363d3cef44b257d50  3338552.data
85e09e18fd495599041e13b4197e1746  3339443.data
0c72004eae0131d52817f23faf8a46a7  3352440.data
26347f93721e7ac49134a17104f56090  3366757.data
26973e301da4948a0016765e40700e8c  3391734.data
c8e4675cda3aa367d523a471bb205fba  3444255.data
7bf5ea753d4cc056b9462a02ac51b160  3494372.data
a2c6562f7f43aaa0e636cc1995b7ee3d  455212.data
d5c91b007dac3a5c6317f8a8833f9304  677136.data
65c0dcd1e7e9f8f87a8e9fb706eb8768  ITEM_20121024_754_WIN_P08AAH.exe
$ file *
1293930.data:                     MS-DOS executable
1294980.data:                     data
2771193.data:                     PE32 executable (native) Intel 80386, for MS Windows
2779874.data:                     PE32+ executable (native) x86-64, for MS Windows
2789142.data:                     PE32 executable (console) Intel 80386 (stripped to external PDB), for MS Windows
2935778.data:                     PE32+ executable (console) x86-64 (stripped to external PDB), for MS Windows
3078639.data:                     MS-DOS executable
3083039.data:                     PE32 executable (GUI) Intel 80386, for MS Windows
3338552.data:                     ASCII text, with CRLF line terminators
3339443.data:                     PE32 executable (native) Intel 80386, for MS Windows
3352440.data:                     PE32+ executable (native) x86-64, for MS Windows
3366757.data:                     PE32 executable (DLL) (GUI) Intel 80386, for MS Windows
3391734.data:                     PE32 executable (GUI) Intel 80386, for MS Windows
3444255.data:                     PE32 executable (GUI) Intel 80386, for MS Windows
3494372.data:                     PE32 executable (DLL) (GUI) Intel 80386, for MS Windows
455212.data:                      PE32 executable (DLL) (console) Intel 80386, for MS Windows
677136.data:                      data
ITEM_20121024_754_WIN_P08AAH.exe: PE32 executable (GUI) Intel 80386, for MS Windows
This is where I get a bit stuck. There is clearly a bunch of WinFlash stuff that Wine kind-of recognises, but so far I haven't managed to figure out how I might go about flashing this from a DOS boot disk. So far I know it's a "Phoenix SecureCore Tiano" based BIOS, and there is some indication that there is a UEFI app to flash the BIOS, but unfortunately I didn't set the laptop up with UEFI (note to anyone setting this up; probably a good idea to do that). I believe that if you have Windows, you can halt the install part-way through and see these files extracted in a temp directory. Possibly if we can put some file-names to the blobs it might help. There may also be a much easier way to do this that I'm completely missing. If anything comes up, I'll update this post; hopefully a future Googlenaut who enjoys BIOS hacking will drop a comment... Update 2012-11-27 I'm unfortunately less optimistic about being able to update this. Certainly the files identified above as MS-DOS executable are EFI binaries; however they are both 32-bit binaries. You can easily get an EFI shell up and running by putting a 64-bit EFI shell binary on a FAT formatted USB disk in the efi/boot/bootx64.efi but it will not run either of those binaries, presumably because they're 32-bit. A 32-bit EFI binary doesn't seem to be recognised for boot, so no luck there. A comment also mentioned some issues with Samsung's and UEFI boot in this bug though it's not clear what models are affected. Another comment mentioned binwalk which also does a nice job of finding the embedded zip streams. 
$ strings ./1293930.data
...
RSDS
D:\flash\Source\ENV\src\Efi863\edk\phoenix\edk\Sample\Platform\DUET\ldr16\IA32\oemslp20.pdb
oemslp20.dll
InitializeDriver
2n3u3
$ strings ./3078639.data
en-us;zh-Hans
slp20.marker
slp20.size
slp20.offset
slp20.offset2
read marker fail!
Marker file '%s''s size(%d)!=%d
Not a valided OemMarker!
Update image data error.
marker file is updated.
marker file size too big!
Not a valided OemMarker in ROM.
Update image data error.
SLP marker is reserved.
-PROT
Prot flag is found, mProgFlag is true.
Prot flag is not found, mProgFlag is false.
Please specify input file name.
-PROT
slpFile
OEM Activation 2.0 processing
Failed to Locate Flash Support protocol.
...
D:\flash\Source\ENV\src\Efi863\edk\phoenix\edk\Sample\Platform\DUET\ldr16\IA32\SLP20.pdb

Cyril Brulebois: Another month, another beta

Today s recipe: Result: Debian Installer 7.0 Beta4 release! Speaking of which, shameless plug: I'm giving a Debian Installer talk at mini-DebConf Paris this sunday.

Paul Tagliamonte: update on dput-ng & debuild.me

I ve been working (although; slowly) on dput-ng. I need to finish dirt (a tool to modify the config files, sorta like how git works at times), but it s otherwise mostly in the state it will be in upon our upload to unstable. good-intentioned co-maintainers and contributors are welcome. Code s in collab-maint, be sure to run big changes through us over in #torabora on irc.oftc.net. I ve also spent some time on debuild.me, and I ve written out most of the krufty bits, more changes to come. If anyone has ARM hardware suggestions, I m open to them, but I m thinking (from some debian-arm advice) that it d be best to wait for the v8 goodies to drop. Godspeed!

21 November 2012

Axel Beckert: Suggestions for the GNOME Team

Thanks to Erich Schubert s blog posting on Planet Debian I became aware of the 2012 GNOME User Survey at Phoronix. Like back in 2006 I still use some GNOME applications, so I do consider myself as GNOME user in the widest sense and hence I filled out that survey. Additionally I have to live with GNOME 3 as a system administrator of workstations, and that s some kind of usage, too. ;-) The last question in the survey was Do you have any comments or suggestions for the GNOME team? Sure I have. And since I tried to give constructive feedback instead of only ranting, here s my answer to that question as I submitted it in the survey, too, just spiced up with some hyperlinks and highlighting:
Don t try to change the users. Give the users more possibilities to change GNOME if they don t agree with your own preferences and decisions. (The trend to castrate the user was already starting with GNOME 2 and GNOME 3 made that worse IMHO.) If you really think that you need less configurability because some non-power-users are confused or challenged by too many choices, then please give the other users at least the chance to enable more configuration options. A very good example in that hindsight was Kazehakase (RIP) who offered several user interfaces (novice, intermediate and power user or such). The popular text-mode web browser Lynx does the same, too, btw. GNOME lost me mostly with the change to GNOME 2. The switch from Galeon 1.2 to 1.3/2.0 was horrible and the later switch to Epiphany made things even worse on the browser side. My short trip to GNOME as desktop environment ended with moving back to FVWM (configurable without tons of clicking, especially after moving to some other computer) and for the browser I moved on to Kazehakase back then. Nowadays I m living very well with Awesome and Ratpoison as window managers, Conkeror as web browser (which are all very configurable) and a few selected GNOME applications like Liferea (luckily still quite configurable despite I miss Gecko s about:config since the switch to WebKit), GUCharmap and Gnumeric. For people switching from Windows I nowadays recommend XFCE or maybe LXDE on low-end computers. I likely would recommend GNOME 2, too, if it still would exist. With regards to MATE I m skeptical about its persistance and future, but I m glad it exists as it solves a lot of problems and brings in just a few new ones. Cinnamon as well as SolusOS are based on the current GNOME libraries and are very likely the more persistent projects, but also very likely have the very same multi-head issues we re all barfing about at work with Ubuntu Precise. (Heck, am I glad that I use Awesome at work, too, and all four screens work perfectly as they did with FVWM before.)
Thanks to Dirk Deimeke for his (German written) pointer to Marcus Moeller s interview with Ikey Doherty (in German, too) about his Debian-/GNOME-based distribution SolusOS.

Ian Campbell: Consolidating Qcontrol Configuration Files

A little while ago Michele Cane filed Debian bug #689912 against qcontrol asking that the package install the correct configuration file for a TS-419P II, a newer device which has an LCD. It turns out that to support devices with LCDs properly we need to probe a GPIO line in order to figure out if an LCD is attached or if a serial console is in use (since the two are mutually exclusive on this hardware, when you attach a serial console you must toggle a jumper too). This actually turns out to be rather trivial since qcontrol's configuration files are actually simple Lua programs and the state of the GPIO lines can be accessed via sysfs and so we can read the state directly from the configuration file itself. While looking into this I happened to notice that the various board-specific configuration files are actually very similar and that the differences can all be detected by a combination of the Hardware field in /proc/cpuinfo and the GPIO lines. So I started looking into whether I could write a single consolidated qcontrol.conf file to replace the various variant specific files. It turns out to be quite possible, the resulting consolidated file has been posted to the bug log (see also my mail). The danger with configuration files which are also fully-fledged programming languages is that there is a temptation to write more and more complex configuration files with the danger that the primary purpose of the file (configuration) can be obscured. I think in this case it is a close call but on balance I think the downsides outweigh the advantages, so I've uploaded qcontrol 0.4.2+svn-r40-2 which simply adds LCD support to the relevant board specific configuration file. In process of doing so I seem to have fallen into a trap which seems to catch out many sbuild users at least once and uploaded a package with "UNRELEASED" still in the changelog. To try and save myself (and others) some blushes in the future I've filed Debian bug #693841 (wishlist) against dput to see if it can catch this case, I've also added to my prerelease checklist. As it happens my own TS-419P II arrived today. I intend to use it for second tier storage (mythtv recordings, music, mirrors) as well as light server duties (MTA, internal DNS etc) which should allow me to turn off the existing PC in the cupboard under the stairs which is getting a bit long in the tooth and starting to become a bit unreliable (I also suspect its costing a fortune to run).

Sandro Tosi: Attending the Codecademy

You've probably already got it, I'm surveying several sites to improve programming skills. This episode is about Codecademy.

It's a very well done site, for people that want to learn a language. It has a Python track, along with several others: Ruby, JQuery, Javascript & so on.

You'll be required to actually write code and run it! yes, the code you write is then executed in a web "interpreter" (modified for educational purposes) and the output displayed on screen. In a section is also possible to write to files and have their contents shown on another tab.

I'd encourage you to start from it if you never saw Python and you're willing to learn if from the ground up.

Michal &#268;iha&#345;: Weblate available as BitNami stack

Weblate is now available for your cloud or virtual machines - BitNami has published Weblate stack. BitNami stack allows you to install native application on Linux or Mac OS X as well as provides images for virtual machines or to be run within cloud (some of these options are still waiting to be built). Also I wanted to finally release SUSE Studio images, but all I get out of that are HTTP 500 errors (whenever I tried since Friday). Luckily today I at least managed to build one image to test. This allowed me to reproduce bug with broken registration as mailserver was missing in the image.

Filed under: English Suse Weblate 0 comments Flattr this!

David Paleino: Wicd .deb packages

Hello world, it's been a long time since I last posted something. Today, I want to let the world know about the availability of Debian packages for wicd. Since the release cycle of wicd is somewhat slow, I decided to provide automatically-built Debian packages for the latest revision of the upstream repository. The automatic build process is possible thanks to Jenkins and the great jenkins-debian-glue, by Michael Prokop. Here's the APT snippet, for those who dare: 
# For the "upstream" version of wicd
deb http://jupiter.hanskalabs.net/debian/ wicd main
The repository is signed with a separate GnuPG key, which I signed with my main keys. You can download it or retrieve it from a keyserver, then you should add it to your APT keyring: 
$ gpg --keyserver pgp.mit.edu --recv-keys 4D00F190
# gpg --export 4D00F190   apt-key add -
Obviously these builds are not guaranteed to work :) but, since I myself use these autobuilt packages, I usually try to fix problems as soon as I notice them. If you find bugs, or have proposals to improve wicd, please report them on launchpad!

Erich Schubert: Phoronix GNOME user survey

While not everybody likes Phoronix (common complaints include tabloid journalism), they are doing a GNOME user survey again this year. If you are concerned about Linux on the desktop, you might want to participate; it is not particularly long.
Unfortunately, "the GNOME Foundation still isn't interested in having a user survey", and may again ignore the results; and already last year you could see a lot of articles along the lines of The Survey That GNOME Would Rather Ignore. One more reason to fill it out.

Dirk Eddelbuettel: Rcpp attributes: A simple example 'making pi'

We introduced Rcpp 0.10.0 with a number of very nice new features a few days ago, and the activity on the rcpp-devel mailing list has been pretty responsive which is awesome. But because few things beat a nice example, this post tries to build some more excitement. We will illustrate how Rcpp attributes makes it really easy to add C++ code to R session, and that that code is as easy to grasp as R code. Our motivating example is everybody's favourite introduction to Monte Carlo simulation: estimating . A common method uses the fact the unit circle has a surface area equal to . We draw two uniform random numbers x and y, each between zero and one. We then check for the distance of the corresponding point (x,y) relative to the origin. If less than one (or equal), it is in the circle (or on it); if more than one it is outside. As the first quadrant is a quarter of a square of area one, the area of the whole circle is -- so our first quadrant approximates over four. The following figure, kindly borrowed from Wikipedia with full attribution and credit, illustrates this: Example of simulating pi Now, a vectorized version (drawing N such pairs at once) of this approach is provided by the following R function. 
piR <- function(N)  
    x <- runif(N)
    y <- runif(N)
    d <- sqrt(x^2 + y^2)
    return(4 * sum(d < 1.0) / N)
And in C++ we can write almost exactly the same function thanks the Rcpp sugar vectorisation available via Rcpp: 
#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
double piSugar(const int N)  
    RNGScope scope;		// ensure RNG gets set/reset
    NumericVector x = runif(N);
    NumericVector y = runif(N);
    NumericVector d = sqrt(x*x + y*y);
    return 4.0 * sum(d < 1.0) / N;
Sure, there are small differences: C++ is statically typed, R is not. We need one include file for declaration, and we need one instantiation of the RNGScope object to ensure random number draws remain coordinated between the calling R process and the C++ function calling into its (compiled C-code based) random number generators. That way we even get the exact same draws for the same seed. But the basic approach is identical: draw a vector x and vector y, compute the distance to the origin and then obtain the proportion within the unit circle -- which we scale by four. Same idea, same vectorised implementation in C++. But the real key here is the one short line with the [[Rcpp::export]] attribute. This is all it takes (along with sourceCpp() from Rcpp 0.10.0) to get the C++ code into R. The full example (which assumes the C++ file is saved as piSugar.cpp in the same directory) is now: 
#!/usr/bin/r
library(Rcpp)
library(rbenchmark)
piR <- function(N)  
    x <- runif(N)
    y <- runif(N)
    d <- sqrt(x^2 + y^2)
    return(4 * sum(d < 1.0) / N)
 
sourceCpp("piSugar.cpp")
N <- 1e6
set.seed(42)
resR <- piR(N)
set.seed(42)
resCpp <- piSugar(N)
## important: check results are identical with RNG seeded
stopifnot(identical(resR, resCpp))
res <- benchmark(piR(N), piSugar(N), order="relative")
print(res[,1:4])
and it does a few things: set up the R function, source the C++ function (and presto: we have a callable C++ function just like that), compute two simulations given the same seed and ensure they are in fact identical -- and proceed to compare the timing in a benchmarking exercise. That last aspect is not even that important -- we end up being almost-but-not-quite twice as fast on my machine for different values of N. The real takeaway here is the ease with which we can get a C++ function into R --- and the new process completely takes care of passing parameters in, results out, and does the compilation, linking and loading. More details about Rcpp attributes are in the new vignette. Now enjoy the .

Update:One somewhat bad typo fixed.

Update:Corrected one background tag.

Axel Beckert: zutils: zcat and friends on Steroids

I recently wrote about tools to handle archives conveniently. If you just have to handle compressed text files, there are some widely known shortcut commands to mimic common commands on files compressed with a specific compression format.
gzip bzip2 lzma xz
cat zcat bzcat lzcat xzcat
cmp zcmp bzcmp lzcmp xzcmp
diff zdiff bzdiff lzdiff xzdiff
grep zgrep bzgrep lzgrep xzgrep
egrep zegrep bzegrep lzegrep xzegrep
fgrep zfgrep bzfgrep lzfgrep xzfgrep
more zmore bzmore lzmore xzmore
less zless bzless lzless xzless
In Debian and derivatives, those tools are part of the according package for that compression utility, i.e. the zcat command is part of the gzip package and the xzfgrep command is part of the xz-utils package. But despite this matrix is quite easy to remember, the situation has a few drawbacks: This is where the zutils project comes in: zutils provides the functionality of most of these utilities, too, but with one big difference: You don t have to remember, think about or type which compression method has been used for your data, just use zcat, zcmp, zdiff, zgrep, zegrep, or zfgrep and it works independently of what compression method has been used if any or if there are different compression types mixed in the parameters to the same command: 
$ zfgrep foobar bla.txt fnord.gz hurz.xz quux.lz bar.lzma
Especially if you use logrotate and let logrotate compress old logs, it s very comfortable that one command suffices to concatenate all the available logfiles, including the current uncompressed one: 
$ zcat /var/log/syslog*
Additionally, zutils versions of these tools also support lzip-compressed files. The zutils package is available in Debian starting with Wheezy and in Ubuntu since Oneiric. When being installed, it replaces the original z* utilities from the gzip package by diverting them away. The only drawback so far is that there neither a zless nor a zmore utility from the zutils project, so zless bla.txt fnord.gz hurz.xz quux.lz bar.lzma will not work as expected even after installing zutils as it is still the one from the gzip package and hence it will show you just the first two files in plain text, but not the remaining ones.

20 November 2012

Jon Dowland: Waterstones

In May this year, in a desperate bid to bail water out of a sinking ship, HMV group sold off the Waterstones chain of bookstores. I'm fond of reading so naturally I visit Waterstones from time to time. (but not exclusively.) For many years, their promotions were unanimously structured as "3 for 2" offers: find three books in the promotion, in-store, and get the cheapest of the three for free. I hated these promotions. I always found it very challenging to find three books in the promotion that I wanted. If I was visiting to buy a specific book and found it in the promotion, on more than one occasion I left the shop empty handed: I wasn't prepared to pay full price for a book in a promotion and not get the benefit of the promotion. Since being sold, Waterstones seem to have made a lot of changes. Many new hardbacks from popular authors have debuted at a discount for a short period (Rowling, Pratchett). I've found many more discounted books not tied to others in 3-for-2-style offers, sometimes window-display stock at half price, a month or so after release. They started a loyalty-card scheme, with a 10 gift card the prize you reach once you've spent 100. (I wonder if such schemes are examples of a token economy?) Finally, they've tentatively started to explore putting cafes in their branches. The one in Newcastle is best described as 'fledgling', but it's nice to have one more place to escape for a cup of tea at lunchtimes. The cafe, as well as a very well stocked collection of magazines, were the two killer features of the sadly- defunct Borders bookseller chain. For years before we got our own Borders in the North East, I used to enjoy the York branch if I was passing. I actually managed to fill a loyalty card this year, so clearly their change in attitude has worked on me! I'm generally not a fan of gift cards, especially in today's climate, so I quickly spent it. I hold an American Express credit card, which earns me cashbask on purchases which I make with it. I think the rate is about 1%. However, I can opt to receive the cashback in the form of gift vouchers. If I do so, I get them to the value of 110% my cashback balance. One of the retailers in on the scheme are Waterstones. I'm tempted

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